A need exists for it to be possible to bring about the said prevention in a technically simple and economically advantageous way. One way of approaching the problem is to arrange the cases of the ammunition units in such a way that they prevent electrical energy transmission, but this is not an entirely advantageous approach as it complicates the construction of the ammunition unit and moreover makes it more expensive. Furthermore, such insulated cases are easy to damage during handling and are difficult to manufacture. The present invention aims to solve, or at least considerably reduce, the said problem of undesirable electricity transmission and proposes inter alia that the barrel is to be made in such a way on its inner surface which lies opposite the ammunition case in the firing position of the ammunition unit that the ammunition unit can have a conventional design, that is to say the ammunition types existing today for the weapon concerned can be fired without difficulty, and in particular without the barrel or the rest of the body of the weapon becoming live when firing takes place.